Multi-layer wraparound heat shrink sleeve

Abstract

A multiple layer wraparound sleeve having a heat shrinkable backing layer and at least one functional layer has the functional layer as a discrete sheet which is connected to one end of the backing layer, and is of at least sufficient length that, when the sleeve is wrapped around the pipe or other substrate at least twice, the functional layer sheet wraps around the substrate first with its ends overlapping and the backing layer wraps around the functional layer sheet with its ends overlapping. This allows wrappings of reduced thickness to be employed without problems of voids occurring between the functional layer and the substrate.

We claim: 
     
       1. A multiple layer wraparound heat shrinkable sleeve comprising a sheet of dimensionally heat unstable flexible material having longitudinally spaced end portions capable of being brought into overlapping relation when said sheet is applied to an article in wrapping relation thereto, the material of said sheet being crosslinked and weldable to itself and having been stretched in the longitudinal direction from an originally heat stable form to a dimensionally heat unstable form capable of moving in the direction of its original form by the application of heat alone, one of said end portions having connected thereon at least one flexible auxiliary sheet comprising a functional material and of length at least sufficient to encircle the article and the other of said end portions having an exposed portion directly overlapping on and weldable to said one end portion when the auxiliary sheet is wrapped around the article with its end portions overlapping and the dimensionally heat unstable sheet is wrapped over the auxiliary sheet with its end portions overlapping. 
     
     
       2. A sleeve as claimed in claim 1 wherein the auxiliary sheet comprises a sheet of heat activable a sealant or adhesive. 
     
     
       3. A sleeve as claimed in claim 2 wherein said sheet of sealant or adhesive is a self supporting film. 
     
     
       4. A sleeve as claimed in claim 2 wherein said sheet of heat activable sealant or adhesive is laminated to a carrier sheet. 
     
     
       5. A sleeve as claimed in claim 1 comprising a further flexible auxiliary sheet connected on an end of the first mentioned auxiliary sheet opposite the dimensionally unstable sheet and of length at least sufficient to encircle said article and overlap, whereby a three-layer wrapping may be formed. 
     
     
       6. A sleeve as claimed in claim 5 wherein said first mentioned auxiliary sheet comprises a longitudinally heat shrinkable and fusible sheet and said further auxiliary sheet comprises a heat activable sealant or adhesive. 
     
     
       7. A sleeve as claimed in claim 6 wherein said sheet of dimensionally heat unstable material is non-adherent to and is strippable from said fusible sheet. 
     
     
       8. A sleeve as claimed in claim 5 wherein said first mentioned auxiliary sheet comprises a sealant or adhesive and said further auxiliary sheet comprises a flexible metal sheet. 
     
     
       9. A sleeve as claimed in claim 5 wherein said first mentioned auxiliary sheet comprises a non-crosslinked electrically insulative polymeric material, said further flexible auxiliary sheet comprises a non-crosslinked polymeric composition capable of modifying lines of electric field, and said heat shrinkable sheet comprises a crosslinked semi-conductive composition capable of providing an outer screen on a high voltage cable construction. 
     
     
       10. A sleeve as claimed in claim 1 wherein said at least one auxiliary sheet is a different width from said dimensionally heat unstable sheet. 
     
     
       11. A sleeve as claimed in claim 10 wherein said auxiliary sheet is narrower than said dimensionally heat unstable sheet. 
     
     
       12. A sleeve as claimed in claim 1 wherein said at least one auxiliary sheet comprises a mesh of reinforcing fibres. 
     
     
       13. A sleeve as claimed in claim 1 including a hold down adhesive portion on the dimensionally heat unstable sheet adjacent said exposed portion of said other end portion, for initially holding said other end portion overlapped on said one end portion.